WEEK 5 PART 1
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326 Terms
Page 5:
What is a biological response ?
a reaction that occurs in an organism as a result of a stimulus or change in its environment
Page 5:
At what levels can biological responses occur ?
Biological responses can occur at cellular, tissue, organ or whole organism levels
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what are the main purposes of biological responses ?
biological responses help organisms maintain homeostasis, respond to threats, and adapt to changing environmental conditions
Page 6:
what determines a cells biological response ?
a cells biological response depends on multiple extracellular signals
Page 6:
what are the four main types of cellular biological responses shown in the diagram ?
1) survive
2) grow + divide
3) differentiate
4) die (aptosis)
Page 6:
what happens in the “survive” cellular response ?
the cell continues to live without dividing or changing its form, maintaining its current state and functions
Page 6:
what happens in the “grow + divide” cellular response ?
the cell increases in size and then undergoes cell division (mitosis) resulting in two daughter cells
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what happens in the “differentiate” cellular response ?
the cell changes its form and function to become a specialised cell type with a specific role in the organism
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what happens in the “die” cellular response ?
the cell undergoes programmed cell death (Aptosis), which is a controlled process where the cell kills itself
Page 6:
what is an apoptotic cell ?
an apoptotic cell is a cell that is undergoing programmed cell death, characterised by cell shrinkage, nuclear fragmentation and membrane blebbing
Page 6:
why do cells need different response options to extracellular signals ?
different response options allow for organisms development, tissue maintenance, defence against damage and adaptation to changing environments
Page 8:
what are the four main forms of cell signalling shown in the diagram ?
1) contact dependent
2) paracrine
3) synaptic
4) endocrine signalling
Page 8:
what is contact dependent signalling ?
a form of signalling where the signalling cell and the target cell make direct physical contact through membrane bound signal molecules
Page 8:
what are membrane bound signal molecules in contact dependent signalling ?
proteins embedded in the cell membrane that interact directly with receptors on adjacent cells, allowing for communication only between cells that physically touch
Page 8:
what is paracrine signalling ?
a form of signalling where the signalling cell releases local mediators that affect nearby target cells
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what are the local mediators in paracrine signalling ?
chemical messengers that are released by a signalling cell and diffuse a short distance to affect nearby target cells
Page 8:
what is synaptic signalling ?
a specialised form of cell signalling where a neuron releases neurotransmitters across a synapse to communicate with a target cell
Page 8:
What components are involved in synaptic signalling ?
the neurone cell body, axon, synapse, neurotransmitters and the target cell with receptors
Page 8:
What is endocrine signalling ?
a form of signalling where specialised endocrine cells release hormones into the bloodstream to affect target cells throughout the body
Page 8:
how do hormones reach their target cells in endocrine signalling ?
hormones travel through the bloodstream to reach target cells that have specific receptors for that hormone, allowing for long distance signalling
Page 8:
what is the key difference between paracrine and endocrine signalling ?
paracrine signalling affects nearby cells through local diffusion, while endocrine signalling affects distant cells through hormone transport in the bloodstream
Page 9:
what are the key characteristics of synaptic signalling ?
synaptic signalling is fast, precise, and involves high local concentration of neurotransmitters
Page 9:
what are the key characteristics of endocrine signalling ?
endocrine signalling is slow and acts at very low hormone concentrations
Page 9:
how do multiple neurons communicate with their target cells in synaptic signalling ?
multiple neurons (A,B,C) can form specific connections with multiple target cells (A,B,C), allowing for precise and selective communication
Page 9:
how do hormones from different endocrine cells reach their target cells ?
multiple endocrine cells (A,B,C) release hormones into the bloodstream, which then circulate and bind to specific receptors on their target cells
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why is synaptic signalling considered “fast and precise” ?
because neurotransmitters are released directly at the synapse in high concentrations, creating an immediate and targeted effect on specific recipient cells
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why can endocrine signalling function at “very low concentrations” ?
because target cells have highly specific receptors that can detect and respond to small amounts of hormones in the bloodstream
Page 9:
what determines which target cells respond to which signals in both systems ?
In both systems, the presence of specific receptors on target cells determines which cells respond to particular neurotransmitters or hormones
Page 9:
what is the main difference in signal pathway between synaptic and endocrine signalling ?
synaptic signalling uses direct neuron to target connections via synapses, while endocrine signalling uses the bloodstream as a transport system to reach distant target cells
Page 10:
How can extracellular signals affect the behavior of a target cell?
Extracellular signals can act either slowly or rapidly to change target cell behavior through different intracellular pathways.
Page 10:
What is the first step in cell signaling?
The extracellular signal molecule binds to a cell-surface receptor protein.
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What are the two main timing categories for cell signaling responses?
Fast responses (occurring in seconds to minutes) and slow responses (occurring in minutes to hours).
Page 10:
What cellular changes occur in the fast signaling pathway?
Fast signaling leads to altered protein function, which affects cytoplasmic machinery and ultimately changes cell behavior.
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What cellular changes occur in the slow signaling pathway ?
Slow signaling affects DNA and RNA, leading to altered protein synthesis, which changes cytoplasmic machinery and ultimately cell behavior.
Page 10:
What is altered protein function in cell signaling?
Altered protein function occurs when existing proteins change their activity through modifications like phosphorylation, without making new proteins.
Page 10:
What is altered protein synthesis in cell signaling?
Altered protein synthesis involves changes in gene expression, where the cell makes new proteins by transcribing DNA to RNA and translating RNA to protein.
Page 10:
How do both fast and slow signaling pathways ultimately affect the cell?
Both pathways eventually lead to altered cytoplasmic machinery, which results in changed cell behavior.
Page 10:
Why does the pathway involving gene expression (DNA → RNA → protein) take longer?
This pathway takes longer (minutes to hours) because it requires multiple steps: activation of transcription factors, gene transcription, RNA processing, and protein translation.
Page 10:
What connects an extracellular signal to an intracellular response?
The cell-surface receptor protein serves as the connection, translating the external signal into internal signaling pathways.
Page 11:
What are gap junctions?
Gap junctions are specialized channels that allow neighboring cells to share signaling information by permitting small molecules to pass freely between them.
Page 11:
What types of molecules can pass through gap junctions?
Small molecules such as calcium and cyclic AMP (second messengers) can pass freely through gap junctions.
Page 11:
What is the main function of gap junctions in cell signaling?
Gap junctions allow direct communication between adjacent cells by creating channels that enable the exchange of small signaling molecules.
Page 11:
What are second messengers in relation to gap junctions?
Second messengers, like cyclic AMP, are intracellular signaling molecules that can pass through gap junctions to coordinate responses between neighboring cells.
Page 11:
Why is calcium important in gap junction communication?
Calcium is a critical signaling molecule that can pass through gap junctions to coordinate cellular activities like muscle contraction, secretion, and metabolic processes between connected cells.
Page 11:
How do gap junctions differ from other forms of cell signaling?
Gap junctions provide direct cytoplasmic connections between cells, allowing for immediate signal transmission without requiring receptor-mediated processes or extracellular messengers.
Page 11:
What is the significance of gap junctions in tissue function?
Gap junctions allow groups of cells to function as coordinated units by sharing signaling molecules, which is essential in tissues requiring synchronized activity (like heart muscle).
Page 12:
What is the first step in the simplified intracellular signaling pathway?
An extracellular signal molecule binds to a receptor protein in the plasma membrane of the target cell.
Page 12:
What happens after a receptor protein is activated by an extracellular signal?
The receptor activates a cascade of intracellular signaling proteins (shown as square, triangle, and circle shapes in the diagram).
Page 12:
What are the three main types of effector proteins in this signaling pathway?
Metabolic enzymes, gene regulatory proteins, and cytoskeletal proteins.
Page 12:
What cellular change results from activation of metabolic enzymes?
Activation of metabolic enzymes leads to altered metabolism in the cell.
Page 12:
What cellular change results from activation of gene regulatory proteins?
Activation of gene regulatory proteins leads to altered gene expression.
Page 12:
What cellular change results from activation of cytoskeletal proteins?
Activation of cytoskeletal proteins leads to altered cell shape or movement.
Page 12:
What are the three main outcomes of the intracellular signaling pathway shown?
1) Altered metabolism, 2) Altered gene expression, and 3) Altered cell shape or movement.
Page 12:
What is the purpose of intracellular signaling proteins in a signaling pathway?
Intracellular signaling proteins relay and amplify the signal from the receptor to the appropriate effector proteins.
Page 12:
How does a single signal lead to multiple cellular changes?
A single signal can activate multiple branches of the signaling pathway, leading to activation of different types of effector proteins that cause different cellular changes.
Page 13:
What are the two main types of receptors for extracellular signaling molecules?
Cell-surface receptors and intracellular receptors.
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Which type of signaling molecules bind to cell-surface receptors?
Hydrophilic (water-soluble) signal molecules bind to cell-surface receptors.
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Why can't hydrophilic signal molecules cross the plasma membrane?
Hydrophilic molecules cannot pass through the hydrophobic lipid bilayer of the plasma membrane, so they must bind to receptors on the cell surface.
Page 13:
Which type of signaling molecules bind to intracellular receptors?
Small hydrophobic signal molecules bind to intracellular receptors.
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How do hydrophobic signal molecules reach intracellular receptors?
Hydrophobic signal molecules can diffuse through the plasma membrane, and sometimes they are transported by carrier proteins.
Page 13:
Where are intracellular receptors typically located?
Intracellular receptors are typically located in the cytoplasm or nucleus of the target cell.
Page 13:
What determines whether a signaling molecule will use a cell-surface or intracellular receptor?
The chemical properties of the signal molecule determine the receptor type: hydrophilic (water-soluble) molecules use cell-surface receptors, while small hydrophobic molecules use intracellular receptors.
Page 13:
Give examples of signaling molecules that use intracellular receptors.
Steroid hormones (like estrogen, testosterone), thyroid hormones, vitamin D, and retinoic acid use intracellular receptors.
Page 13:
Give examples of signaling molecules that use cell-surface receptors.
Proteins, peptides, amino acids, and charged molecules like epinephrine (adrenaline) and neurotransmitters use cell-surface receptors.
Page 14:
What is the role of nitric oxide (NO) in cell signaling?
Nitric oxide acts as a signaling molecule that causes relaxation of smooth muscle cells, particularly in blood vessels.
Page 14:
How is nitric oxide produced in endothelial cells?
Nitric oxide is produced when activated nerve terminals release acetylcholine, which activates nitric oxide synthase (NOS) in endothelial cells. NOS converts arginine to nitric oxide.
Page 14:
What property of nitric oxide allows it to move between cells?
Nitric oxide can rapidly diffuse across cell membranes due to its small size and lipid solubility
Page 14:
What enzyme does nitric oxide activate in smooth muscle cells?
Nitric oxide binds to and activates guanylyl cyclase in smooth muscle cells.
Page 14:
What second messenger is produced when nitric oxide activates guanylyl cyclase?
Guanylyl cyclase converts GTP to cyclic GMP (cGMP), which acts as a second messenger.
Page 14:
What is the physiological effect of increased cyclic GMP in smooth muscle cells?
Increased cyclic GMP causes rapid relaxation of smooth muscle cells, which leads to vasodilation (widening of blood vessels).
Page 14:
What medical application of this pathway is mentioned in the image?
Nitroglycerin is used in patients with angina to reduce the workload of the heart by causing vasodilation through the nitric oxide pathway.
Page 14:
What is the anatomical relationship between endothelial cells and smooth muscle cells in blood vessels?
Endothelial cells form the inner lining of blood vessels (adjacent to the lumen), while smooth muscle cells form a layer outside the endothelial cells, separated by a basal lamina.
Page 14:
Why is the nitric oxide signaling pathway important for cardiovascular health?
The nitric oxide pathway regulates blood vessel dilation, which controls blood pressure and blood flow to tissues, making it critical for cardiovascular health.
Page 15:
How do most activated cell-surface receptors relay signals inside the cell?
Most activated cell-surface receptors relay signals via small molecules (second messengers) and a network of intracellular signaling proteins.
Page 15:
: What are the main types of second messengers found in the cytosol?
The main second messengers in the cytosol are cyclic AMP (cAMP) and calcium ions (Ca²⁺).
Page 15:
What is an example of a fat-soluble second messenger?
Diacylglycerol is an example of a fat-soluble second messenger.
Page 15:
What is the first step in the cell-surface receptor signaling pathway?
The first step is primary transduction, where an extracellular signal molecule binds to a receptor protein in the plasma membrane.
Page 15:
What is the role of scaffold proteins in cell signaling?
Scaffold proteins help organize signaling components and relay the signal from the activated receptor to downstream signaling proteins.
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What happens during the "transduce and amplify" stage of signaling?
During this stage, the signal is converted to a different form and amplified, creating many activated downstream molecules from a single receptor activation.
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What is the purpose of the "integrate" step in the signaling pathway?
The integrate step combines signals from multiple pathways to coordinate the cellular response based on various inputs.
Page 15:
What happens in the "spread" stage of signaling?
In the spread stage, the signal branches out to affect multiple downstream targets, allowing a single signal to trigger various cellular responses.
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What is the final outcome of the signaling pathway in the nucleus?
The final outcome in the nucleus is effector protein activation and gene transcription, where specific genes are activated in response to the signal.
Page 15:
What are the key stages in cell-surface receptor signaling from beginning to end?
Primary transduction → Relay → Transduce and Amplify → Integrate → Spread → Anchor → Modulate → Effector Protein Activation → Gene Transcription.
Page 16:
What is desensitization in cellular signaling?
Desensitization (adaptation) is a process where target cells become less responsive to an extracellular signal molecule despite its continued presence.
Page 16:
What are the five mechanisms of desensitization shown in the image?
1) Receptor sequestration, 2) Receptor down-regulation, 3) Receptor inactivation, 4) Inactivation of signaling protein, and 5) Production of inhibitory protein.
Page 16:
What happens during receptor sequestration?
During receptor sequestration, activated receptors with bound signal molecules are internalized into endosomes, temporarily removing them from the cell surface.
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What is receptor down-regulation?
Receptor down-regulation occurs when internalized receptors in endosomes are delivered to lysosomes for degradation, permanently reducing receptor numbers.
Page 16:
How does receptor inactivation contribute to desensitization?
Receptor inactivation occurs when receptors remain on the cell surface but are modified (often by phosphorylation) to make them unable to activate signaling pathways.
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What happens in the "inactivation of signaling protein" mechanism?
In this mechanism, components of the signaling pathway downstream of the receptor are inactivated, preventing signal transmission even when the receptor is activated.
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How does the production of inhibitory proteins lead to desensitization?
The signal itself triggers production of inhibitory proteins that block the signaling pathway at various points, creating a negative feedback loop.
Page 16:
Why is desensitization important for cells?
Desensitization allows cells to adapt to persistent signals, prevents overstimulation, enables detection of changes in signal concentration rather than absolute levels, and is crucial for processes like sensory adaptation.
Page 16:
What is the difference between temporary and permanent desensitization mechanisms?
Temporary mechanisms (like receptor sequestration and inactivation) can be quickly reversed, while permanent mechanisms (like receptor down-regulation) require new protein synthesis to restore sensitivity.
Page 17:
What are the four main types of receptors in cell signaling?
Type 1: Ion-channel-linked receptors, Type 2: G-protein-linked receptors, Type 3: Enzyme-linked receptors, and Type 4: Nuclear receptors.
Page 17:
Where are Type 1, Type 2, and Type 3 receptors located in the cell?
Types 1, 2, and 3 receptors are all located in the cell membrane.
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Where are Type 4 receptors located in the cell?
Type 4 receptors (nuclear receptors) are located in the nucleus.
Page 17:
What is the effector mechanism of ion-channel-linked receptors?
Ion-channel-linked receptors function as channels that allow specific ions to flow across the membrane when activated.
Page 17:
What are the effector mechanisms of G-protein-linked receptors?
G-protein-linked receptors can activate either enzymes or channels through G-protein intermediaries.
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What is the effector mechanism of enzyme-linked receptors?
Enzyme-linked receptors have enzymatic activity or directly activate enzymes when bound to their signal molecules.
Page 17:
What is the effector mechanism of nuclear receptors?
Nuclear receptors directly regulate gene transcription when activated.
Page 17:
How do ion-channel-linked receptors couple to their effects?
Ion-channel-linked receptors couple directly to their effects - the receptor itself forms the ion channel.
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Flashcards (909)